In an electrochemical cell, e.g., a battery cell, electric current is carried from a battery electrode foil to a centrally located terminal. The electrode foil can be directly connected to the central terminal, or it can be connected to the central terminal through a current collecting tab. In some conventional energy delivery devices, the orientation of the plane of the foil or tab at the location in which it connects to the central terminal largely coincides with the longitudinal axis of the cell. Employing such a connection requires considerable vertical space in the cell.
Known means of joining electrode tabs using ultrasonic, resistance or other welding methods require that the interior battery cell components, e.g. tabs, be accessible to weld anvils, electrodes, laser beams, etc. Examples of prior joining techniques are disclosed in U.S. patent application Ser. No. 12/135,708, entitled Cap Assembly For a High Current Capacity Energy Delivery Device, which is hereby incorporated by reference.
A commercially available prior art design of a lithium ion battery cell 10 is shown in FIG. 1. The battery cell 10 comprises terminal end 20 and non-terminal end 30. The battery cell 10 is shown with the terminal end 20 removed in FIG. 2. Extension tab 40 is provided to electrically couple the terminal cap 20 to internal workings of the battery cell 10. More specifically, the extension tab 40 serves as a conduit between the negative terminal 50 and the negative current collecting electrode tabs 60, which are positioned beneath washer 70. Although the extension tab is necessary in this configuration, it takes away from the volume of the cell which could otherwise be used to provide a higher capacity battery. The positive terminal 80 is electrically coupled to the cell 10 which maintains a positive potential. A radial weld is made to couple the electrode tabs 60 to core insert 90 and produces weld mark 94.